Dust/particle collecting arrangement for cyclone separators

ABSTRACT

Apparatus is described for separating particulate material from an airstream established by suction. The apparatus comprises a primary separation chamber ( 12 ) in which particles are separated from the airstream therein by centrifugal force, a main particle collecting region ( 14 ) into which the particles separated by the primary separation can fall under gravity, and a secondary separation chamber ( 90 ) downstream of the primary chamber ( 12 ), to which air and particles not separated in the first chamber, pass. An air outlet in the secondary chamber allows air substantially free of particles to exit. An intermediate particle collecting region ( 22 ) is associated with the secondary chamber, in which particles collect after separation by centrifugal force from the air flowing through the secondary chamber ( 90 ). A valve ( 41 ) is provided between the intermediate particle collecting ( 22 ) region and a second particle collecting region ( 14 ), which is closed while air flows through the apparatus but which is opened when airflow ceases, to allow particles in the intermediate region ( 22 ) to pass into the second region

FIELD OF INVENTION

[0001] The invention concerns separators which separate one materialfrom another based on their relative densities. In a domestic context acyclone-based vacuum cleaner is a separator for separating dirt and dustparticles from air. Similar devices are employed in industrial andcommercial processes, in laboratories and in clinical and hospitalenvironments for separating particulate material from fluids—normallyair or gaseous mixture; or particulate material for liquids. Inparticular, but not exclusively the invention is applicable to vacuumcleaners in which one or more cyclones are set up within the apparatusfor the purpose of efficiently separating dust and dirt particles froman incoming airstream.

BACKGROUND TO THE INVENTION

[0002] In the separator/vacuum cleaner shown in PCT/GB98/03306, thecollector 14 receives dust and dirt particles which have been separatedby the secondary cyclone effect in the conical chamber 73. Dust andparticles from the primary cyclone separation effect in the region 13,are collected in region 31 of collector 32, and when the level of thedust and particles in 31 gets close to the flange 21, the collector 32must be emptied.

[0003] For satisfactory operation, the interior of 14 must be keptseparate from 31.

[0004] However in practice it is found that even when 31 is full, thevolume of dust and dirt particles in 14 is a small fraction of that in31, and the useful volume of 32 is very substantially reduced by thesecondary cyclone collection chamber 14.

OBJECT OF THE INVENTION

[0005] It is an object of the present invention to provide an improvedparticle collecting arrangement for collecting particles from twoseparation stages of a multistage air/particle separator.

SUMMARY OF THE INVENTION

[0006] 1. According to the present invention apparatus for separatingparticulate material from an airstream established by suction,comprises:

[0007] (1) a primary separation chamber in which particles are separatedfrom the airstream therein by centrifugal force;

[0008] (2) a main particle collecting region into which the particlesseparated by the primary separation can fall under gravity;

[0009] (3) a secondary separation chamber downstream of the primarychamber, to which air and particles not separated in the first chamber,pass;

[0010] (4) an air outlet in the secondary chamber through which airsubstantially free of particles can exit;

[0011] (5) an intermediate particle collecting region associated withthe secondary chamber, in which particles collect after separation bycentrifugal force from the air flowing through the secondary chamber;

[0012] (6) a valve between the intermediate particle collecting regionand a second particle collecting region, which is closed while air flowsthrough the apparatus but which is opened when airflow ceases to allowparticles in the intermediate region to pass into the second region.

[0013] The second collecting region may be separate from the mainparticle collecting region, but advantageously the main particlecollecting region also comprises the second particle collecting region.

[0014] The valve means is operable manually, or electrically, butpreferably the valve operates in response to the flow of air through theapparatus so as to become closed when the air flow reaches and exceeds agiven rate of flow, and opens when air fluid flow falls below a givenrate of flow.

[0015] The valve may comprise a ball valve comprising a captivelightweight ball which is lifted by the airflow to close an orifice atone end of the secondary chamber, and which will fall back under gravityto open the orifice when the airflow ceases.

[0016] A baffle may be provided downstream of the valve to reduce thetendency for material beyond the valve to be sucked back through thevalve while the air flow is being established.

[0017] A baffle may be located between the intermediate and secondregions to create a tortuous path for particulate material therethrough.

[0018] In either event the baffle may comprise a helix.

[0019] The entry point of the helix may be spaced from the exit from thesecondary separation chamber.

[0020] The gap between the entrance to the helix and the exit from thesecondary separation chamber is in the range 4 to 6.4 mm.

[0021] The helix may have two complete turns.

[0022] Typically a gap of the order of 4 mm exists between the ball andthe valve seating, when open.

[0023] The valve seating may include an annular seal so that when theball is held thereagainst by suction, there is no tendency for air toleak past the ball.

[0024] Alternatively the closure member may present a conical orfrusto-conical surface to an annular seating, which preferably includesan O-ring seal for engagement by the said surface to close the valve.

[0025] A spring may to advantage be provided acting on the ball or otherclosure in a direction to open the valve.

[0026] Preferably a level sensing device is provided in the or eachparticle collecting region to indicate when the contents of thecollecting region has reached a given level, requiring it to be emptied.

[0027] The sensing device typically includes a switch for generating analarm and/or interrupting the power supply to the suction producingmeans.

[0028] The invention is not limited to apparatus for separatingparticles from air but may be employed in apparatus operating in asimilar way to separate particulate material from a liquid (where theparticulate material is more dense than the liquid) or one liquid fromanother liquid (again where there is a difference in density of the twoliquids).

[0029] The invention will now be described, by way of example, withreference to the accompanying drawings, in which:

[0030]FIG. 1 is an elevation partly in cross-section, of a three stagecyclone vacuum cleaner (separator) in which the dust particles from thesecondary stage are collected in a supplementary bin which is separatefrom the bin which collects the dust particles from the primaryseparator;

[0031]FIG. 3 is an elevation partly in cross-section of an alternativepreferred three stage cyclone separator, modified to include a valvesuch as shown in FIG. 2, so as not to require a supplementary dustcollecting bin;

[0032]FIG. 4 is a cross-section through a modified lower end into theflow control valve for sensing when the dust/particle content of the binexceeds a given height;

[0033]FIG. 5 is a cross-sectional elevation of another three stageseparator embodying the invention;

[0034]FIGS. 6 and 6A are a cross-sectional elevation and perspectiveview from below of a preferred ball-valve;

[0035]FIGS. 7 and 8 show a different form of separator and valve.

DETAILED DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 illustrates one embodiment of cyclone vacuum cleaner(separator) of the type to which the present invention can be applied.

[0037] As shown in the drawings, the device comprises a suction inlet 10which can be connected to a hose and dust collecting wand, or to arotating brush assembly such as is located in the base of a domestic orindustrial upright vacuum cleaner.

[0038] The suction inlet enters tangentially a cylindrical enclosuregenerally designated 12 and the upper end of a dust and dirt collectingdrum 14. The lower part 14 is typically a push-bit at 16 to the upperregion 12 and includes a handle 18. When full, the drum 14 is detachedfrom the upper end 12, and emptied. The push-fit must provide a goodsealing joint between 12 and 14 or a separate ring seal must beincluded. from the upper end 12, and emptied. The push-fit must providea good sealing joint between 12 and 14 or a separate ring seal must beincluded.

[0039] The tangential entrance of the air stream causes the incoming airto circulate around the interior of the cylindrical region 12 andbecause of the higher mass of dust particles relative to air particles,the dust and dirt entrained in the air stream tends to migrate to theouter ends of the rotating air stream and fall into the drum 14 whilstrelatively dust free air tends to spiral inwardly to eventually passthrough the plurality of openings such as 20 in the hemispherical dishgenerally designated 22 located axially centrally of the cylindricalregion 12.

[0040] After passing through the holes 20, the air rises into the uppercylindrical cavity 24 from which it exits via port 26 and is conveyed tothe inlet port 28 at the upper end of a conical chamber 30 in which thesecond stage of separation occurs.

[0041] The upper end 32 of the conical housing 30 is itself cylindricaland the entrance 28 communicates tangentially with that cylindricalregion in the same way as inlet 10 communicates with the cylindricalregion 12.

[0042] It will be appreciated that as the height of dust and particlesin the drum 14 begins to rise, there could be a tendency for therotating air stream in the region 12 to draw dust and particles from theheap in the bottom of drum 14, back into the air stream from which theyhave been separated by the centrifugal force in the upper cylindricalregion 12. To reduce this tendency, a hemispherical baffle 34 isprovided so that only a narrow annular region 36 exists through whichthe particles and dust can fall from the rotating air stream in theregion 12, into the drum 14. The baffle 34 serves to separate therotating air stream in the region 12 from the dust and particle contentof the drum 14, and reduces the risk of the dust and particles in 14becoming entrained in the rotating air stream in 12.

[0043] The hemispherical surface 22 merges into the oppositely curvedhemispherical surface of the baffle 34 where they are both joined to thelower end of the conical housing 30.

[0044] The latter therefore provides the central support for the baffle34 and for the hemispherical surface 22 containing the exit apertures20.

[0045] It will be appreciated that the presence of the lower end of theconical housing 30 penetrates and therefore renders incomplete, the twohemispherical surfaces 22 and 34.

[0046] Within the upper cylindrical region 32 is located a turbine showndesignated 38 carried by a central hollow axle 40, the lower end ofwhich is formed with a frusto-conical surface 42 which serves as acyclone starter for the conical chamber 30.

[0047] Air entering the cylindrical region 32 via port 28 causes theturbine to rotate and the rotating air stream set up by the tangentialentrance of port 28 into the cylindrical region 32 causes a downwardlyspiralling cyclone in manner known per se. Dust and particles entrainedin the spiralling air stream tend to be deposited at the lower end ofthe conical chamber 30 where they pass through a circular opening 44into a secondary collecting bin 46 after first circulating around ahelical baffle 48 at the upper end of the secondary bin 46.

[0048] The latter is also conical in configuration and is complementaryto the conical housing 30. The interior of the conical secondary bin 50serves to collect dust and particles separated by the cycloneestablished in the conical chamber 30 but it will be seen that the wallof the secondary bin 46 separates the interior 50 from the annularregion 52 within which the separated dust and particle content from theprimary air stream bin 12, are collected.

[0049] The centre of the helix 48 presents a flat circular end 54 ashort distance below the cylindrical passage 44 leading from the end ofthe conical chamber 30, and typically the diameter of 44 is of the orderof 10 mm and the distance between the open end of 44 and the plate 54 isof the order of a few millimetres. The downwardly ascending spiral ofair within 30, reverses near the lower end 30 to form an upwardspiralling central cyclone (not shown) which moves in the generaldirection of the arrow 56 to pass into and through the hollow interior58 of the axle 40, and to enter a cylindrical region above thecylindrical region 32 housing the turbine 38. The passage from 58 into60 is through windows such as 62 in a frusto-conical shaped spinner 63which is mounted on the axle 40 so as to rotate with the turbine 38.Upper and lower walls of the spinner 64 and 66 respectively are closed,so that air passing into the central region of the spinner 63 can onlyexit through the windows such as 62. Radially extending flanges such as65 located between the windows, impart rotation to the exiting airstream as it enters cylindrical region 60, and the air spirals upwardlythrough the chamber 60 further assisted by a rotating helix 68 mountedon a second horizontal axle 70 which rotates with the spinner 63.

[0050] Air from 58 cannot pass axially into the interior 78 of thesecond hollow axle 70, but has to pass through the windows 62 and aftercirculating around chamber 60, can either pass into the interior 78 ofthe upper axle 70 via holes such as 80 in the wall of the upper axle orcan leave the chamber 60 via exit 82 to re-enter the air stream belowthe spinner 63 via an inlet port 84 located in the cylindrical region 32at the upper end of the conical cyclone chamber 30. The port 84, likeentrance port 28, merges with the cylindrical region 32 in a tangentialsense so that incoming air from 82 will circulate around the cylindricalregion 32 and further assist in rotating the turbine 38 and will mergewith the incoming air stream via 28, to traverse the conical chamber 30once again before proceeding up the centre of 30 as previously describedand enter the region 58.

[0051] Because of the way in which air is collected from the upperchamber 60 via the port 82, any air leaving via port 82 willpreferentially include any dust or heavier than air particles relativeto that near the centre of chamber 60 and therefore the return path to84 will tend to include dust and particles which have not been separatedby the final separation stage in the region 60, whereas air entering theregion 78 via the holes 80 will tend to be free of dust and particles.

[0052] Although not shown in detail, 78 communicates with a suctiondevice 79 such as a fan or turbine driven by an electric motor or thelike, the action of which is to draw air in the direction of the arrow74 from the apparatus shown in the rest of the drawing. It is thissuction effect created by the rotating fan or turbine (not shown) whichestablishes the incoming air stream at 10 and the general flow of airthrough the apparatus as previously described.

[0053] It has been found that apparatus such as shown in FIG. 1 canoperate at a very high efficiency of separation so that very little dustand particle content is left in the air flow leaving 78, and it has beenfound possible to dispense with the filter which is normally located atsuch a position in the vacuum cleaning apparatus just prior to thevacuum inducing fan or turbine. The presence of any such filtersubstantially reduces the air flow and therefore suction effect createdby the fan and/or turbine, and by not having to include such a filter,the air flow through the apparatus, and therefore the air speeds withinthe various rotating air streams and cyclone is increased, and theseparation efficiency enhanced.

[0054] Since the hollow axle 70 rotates with the spinner 63, and it isnot desirable for the wall 86 to rotate, a rotational seal 88 isrequired between the rotating portion 70 and the stationary portion 86.This may for example comprise complementary chamfered end surfacesbetween the two cylindrical walls with bearing material at 90 and 92 asshown in FIG. 1a.

[0055] Although described as a single turbine, 38 may be formed from twosimilar turbine blade assemblies each occupying half the axial length ofthe turbine 38 as shown, and each secured on the axle 40 with the bladesof one turbine staggered by half the pitch of the blades of the otherturbine so as to effectively double the number of blades of the turbineand therefore increase its efficiency.

[0056]FIG. 1b is a cross-section view through the cylindrical region 12of FIG. 1, and shows the tangential inlet 10 and the cylindrical form ofthe wall of the conical chamber 30 where it is sectioned, the smallorifice at the lower end of the chamber 30, and the intermediatecylindrical outline of the wall 22 where the hemispherical surface 22 iscut by the cross-section.

[0057]FIG. 1c is a cross-section through CC in FIG. 1, and shows how theexit port 26 communicates with the cylindrical region 24 and furtherassists in keeping the air mass rotating as it exits into the region 24by virtue of the tangential exit 26 therefrom.

[0058]FIG. 1d is a cross-section on DD in FIG. 1, and shows onearrangement of inlet port 28 and return port 84 in the region of theturbine 38.

[0059]FIG. 1e is similar to FIG. 1d, but shows alternate positions forports 28 and 84 if desired.

[0060] The important criterion is that a rotating air mass in 32 set upas air enters at 28 will tend to swirl past port 84 and continue in thiscircular motion around 32, rather than enter 84. In the same way, airre-introduced into 32 via 84 will likewise be swept into the rotatingairstream induced by air entering by 28, and there will be no tendencyfor the air to enter the port 28 during its rotational movement within32.

[0061] For clarity, the turbine blades are not shown in FIGS. 1d and 1e, but instead the turbine is shown in FIG. 1f. This shows hollow axle40, central region 58 and eight curved turbine blades of which one isdesignated 41. As shown in FIG. 1f, the turbine is viewed from above,since it will be appreciated that air entering region 32 should bedirected against the surface 43 of the blade 41 (and the correspondingsurface of each of the other blades) to induce rotation of the turbine.

[0062] Where two turbines are mounted on the axle 40, each is of thesame configuration as shown in FIG. 1f, but of half the axial depth of38, so that the two will fit within the same axial space, and aremounted so that when viewed axially, the blades of one turbine will beseen to occupy the spaces between the blades of the other. The blades ofthe second turbine if fitted, are shown in dotted outline in FIG. 1f,and one of these is denoted by reference numeral 45.

[0063]FIG. 1g is a cross-section through FIG. 1 on line GG and shows theexit port 82 communicating tangentially with the cylindrical interior 60and the cylindrical wall 70 of the hollow axle on which the helix 68 ismounted, the upper end of which is shown at 69.

[0064] It will be appreciated that the helix is a relatively close fitwithin the cylindrical housing defining the chamber 60.

[0065] Although not shown in the drawing, it has been found advantageousfor the openings 80 in the wall 70 to start a short distance after thebeginning of the helix at the lower end 70 and to terminate a shortdistance prior to the end of the last turn of the helix at the upper endof 70.

[0066] Typically the apertures 80 are circular and have a diameter of1.7 mm and approximately 1200 such holes are formed in the wall 70.

[0067] Typically the helix has an angle in the range 2 to 10°, typically4°.

[0068]FIG. 2 shows a modification to the lower end of the conicalcyclone separation tube 30. The lower end terminates in chamber 31instead of the cylindrical nozzle 44 of FIG. 1, and within the housing31 is located a helix corresponding to item 48 of FIG. 1.

[0069] The gap between the upper surface 54 of the central region of thehelix 40 and the lower end of the conical tube 30 is selected so as toachieve the desired objectives, namely free ingress of dust andparticles in the direction of the arrows 33 and 35 into the helix andthereafter into the lower region of the chamber 31, but minimal transferof dust or particles in the reverse direction.

[0070] A cage 39 extends below the chamber 31 arranged symmetricallyrelative to the valve seat formed by the seal 37. Within the cage is aball 41 which can cooperate with the valve seat seal 37 to close theopening into the chamber 31. The density of the ball is selected so thata rising air stream passing in an upward sense through the cage into thechamber 31 will cause the ball to lift and become a valve closure memberas it seals against the lip seal 37.

[0071] The cage includes a base 43 the internal upper face of which isformed as a shallow pyramid at 45 to space the ball from the base of thecage when air flow is zero, and the ball can fall under gravity to leavethe opening defined by the valve seat seal 37, open.

[0072] When the FIG. 1 apparatus is modified as shown in FIG. 2, thesecondary bin 46 can be dispensed with. The whole of the drum 14 is nowavailable for storing any dust and particles collected by the separationprocess whether in the primary separation stage in the cylindricalregion 12 or in the secondary stage caused by the reverse cyclone effectwithin the conical housing 30.

[0073] The FIG. 2 arrangement enables this since as soon as air flow isestablished in the apparatus, some of the air entering at 10 will divertinto the lower part of the drum 14 and rise up through the cage 39, theopening defined by the valve seat 37, through the helix 48 and into theconical housing 30. However air flow will lift the ball 41 intoengagement with the seal 37 (as shown in dotted outline) to close theopening at the lower end of the chamber 31 and thereafter the apparatuswill operate substantially as described with reference to FIG. 1. Thechief difference is that particles and dust separated by the cycloneeffect in the conical housing 30 will now leave in the direction of thearrows 33 and 35 and after traversing the helix 48 remain in the smallchamber 31. When the air flow ceases as at the end of a cleaningsession, the ball 41 immediately drops to its lower position from theone shown in dotted outline in FIG. 2, and any dust and dirt particlesin the chamber 31 will fall through the opening around the ball, and outthrough the openings in the cage 39, to join the rest of the dust, dirtparticles collected within the main drum 14.

[0074] Whenever the apparatus is powered up again, air flow is onceagain established, and the process is repeated, with the initial closingof the opening by the engagement of the ball 41 with the seal 37, andthe collection of dust and dirt particles in chamber 31. When theapparatus is again powered down, dust and dirt particles collected in 31will again leave the chamber via the now open valve seating and join therest of the dust and dirt particles in the main drum 14.

[0075] The ball 41 and seal 37 therefore represent a one-way valvewhich, in combination with the helix 48, prevents dust and dirtparticles from entering the lower end of the conical housing 30 when airflow is established. This effectively creates a secondary bin for thedust and particles collected from the secondary separation which occursin the conical housing 30, until it is opportune to mix the dirtparticles and dust collected therein with those in the remainder of thedrum 14.

[0076]FIG. 3 illustrates an alternative cyclone separation apparatusalso incorporating the features associated with the primary separationstage and dust collecting bin 14. Thus dust laden air entering at 10 isas before, caused to move in a circular path within region 12. Dustparticles tend to fall towards the bottom of the bin 14 and air withsubstantially less dust particles contained within it passes through thesmall holes 20 and into the manifold region thereabove to exit via 26.

[0077] In the arrangement shown in FIG. 3, the now dust depleted airflow passes into the upper end of an intermediate chamber 90 via inletport 92. As with inlet port 20, inlet port 92 is tangential to thegenerally circular cross-section of the chamber 90 and as before, theincoming air is caused to follow a rotational path which since there isno exit in the upper region of the chamber 90, begins to travel down ahelical path defined by a helix 94 which is a close fit within thechamber 90, around the central hollow stem 96.

[0078] Air flow out of the chamber 90 is via a large number of verysmall holes formed in the wall of the hollow stem 96. The lattercommunicates with an upper chamber 98 within which is located anotherhelix 100 the purpose of which will be described later.

[0079] One of the holes in the wall of the stem 96 is denoted byreference numeral 102. It has been found advantageous that the holesbegin a short distance (measured around the stem) after the helix hasstarted 96, and terminate a short distance (measured around the stem)before the helix finishes.

[0080] In one arrangement, a circumferential length of approximately 15mm of unperforated stem wall exists at one end of the helix andapproximately 40 mm measured circumferentially of unperforated stem wallexists at the other end of the helix, in each case the circumferentiallength being measured from the adjacent end of the helix around thestem.

[0081] Below the last turn of the helix, the stem 96 extends downwardlyin the lower regions of the chamber 90 and terminates in a conicalclosure 104 which may also be apertured.

[0082] The rapidly moving dust particles will tend to fly out to theouter circumferential regions of the helix and continue down into thelower regions of the chamber 90. Thereafter they will pass down throughthe helix 48 and collect in the lower region of the small collectionchamber above the non-return valve formed by the ball 41, and will bereleased into the collecting bin 14 at the end of the vacuuming sessionas described in relation to FIG. 2.

[0083] The air which passes through the small holes 102 and risesthrough the hollow interior of the stem 96 will be further depleted interms of dust and dirt particles and will rise into the upper chamber 98and be deflected by the downwardly extending conical end 106 at thelower end of the cylindrical tube 108 the upper end of whichcommunicates with the source of the vacuum (not shown), such as amotorised fan or turbine.

[0084] Intermediate its ends, a helix 100 extends around the tube 108and is a close fit within the cylindrical housing 98 in a similar waythat the helix 94 occupies chamber 90. However no apertures are formedin the wall of the tube within the turns of the helix. Instead a region110 of the tube between the lower end of the helix and the downwardlyfacing conical closure 106 is formed with a perforated wall containing alarge number of small apertures, one of which is denoted by reference112.

[0085] Air entering the chamber 98 will in part pass through the holes112 and rise upwardly through the tube 108. The air which does circulatewill tend to be that which is in the central region of the air streamwhich has not been significantly deflected by the effect of thedownwardly deflecting cone 106. The effect of the cone has been found tointroduce a further degree of separation in that particle laden air willtend to carry on in a straight line after being deflected by the coneand will tend to enter the helix 100 rather than change direction andenter the small holes 112 in the section 110. Once the particle ladenair has entered the helix, it can only traverse the chamber 98 via thehelix, and leave via exit 114 at the upper end of the chamber 98 fromwhere it is returned to a second or return inlet 116 at the upper end ofthe intermediate chamber 90. There it entrains with the incoming airstream from inlet 92 and any dust particles remaining in the air streamwill tend to be thrown out by the circular motion of the air as itprogresses down the helix 94 once again for collection as described inthe small chamber below the helix 48, leaving clean air to pass throughthe apertures 102.

[0086] Very high separation efficiencies have been achieved usingapparatus such as shown in FIG. 3.

[0087] The lower end of the cage 39 shown in FIG. 2 and in FIG. 3,incorporates a level sensing device such as shown in FIG. 4. As shown inFIGS. 2 and 3, the lower end of the cage 39 comprises a shallow anglefrusto-conical housing and this is shown in more detail in cross-sectionin FIG. 4.

[0088] The interior of the frusto-conical housing 118 houses amicroswitch 122 having an operating arm 124 which if depressed in anupward sense will change the state of the switch.

[0089] A flexible membrane-diaphragm 126 extends across an opening inthe underside of the housing 118. The diaphragm is held in place by acirclip or other retaining device 128 and is designed to be such that ifthe height of the heap of dust and dirt particles in the bin 14 becomessuch as to make contact with and press against the membrane-diaphragm126, the switch will be operated and the contacts will be closed (oropened as the case may be).

[0090] An electrical connection such as 128 connects the switch contactsto a relay or contactor so that if the switch is operated, power isremoved from the suction motor so that the apparatus ceases to function.A warning signal may be generated, either visibly or audibly to indicateto the user that the bin is now full and should be emptied before anyfurther usage occurs.

[0091] Although not shown, signal warning means may be provided on theapparatus preferably of a visible nature to explain by way of a warningmessage or coded sign that the condition exists requiring the bin to beemptied. Typically this may comprise an LED display or a simpleelectromechanically moved vane which moves so as to display adifferently coloured area of the vane in a window, eg a green region ofthe vane is now replaced by a red region indicating that the bin isfull, once the microswitch is operated.

[0092] Although described in relation to the FIGS. 2 and 3 embodiment, alevel sensing device may also be incorporated into either the inner orouter collector 50, 52 of FIG. 1. Where a warning signal is generated,in association with the FIG. 1 arrangement, this conveniently indicateswhether it is the inner or outer collecting bin which has become full.

[0093] In the alternative separator shown in FIG. 5, particle laden airis sucked into inlet 174 once a vacuum is established by operating amotor-driven vacuum producing fan/turbine 176. The incoming airflow isgenerally tangential to the wall of the cylindrical housing 178 and isthereby caused to form a circulating air mass around the region 180, atthe upper end of the housing. Centrally is located a cylindrical vortexinducer 182 which extends into a hemispherical shell 184 containing alarge number of very small openings 186 through which air can pass.

[0094] Below the surface 184 is located a similar but oppositelyconvexly curved shroud 188, which extends almost to the internal wall ofthe housing 178. Centrally of 182 and 184 a frusto-conical tubularsurface 185 extends in an axially downward manner to communicate with anopening 190 in the centre of the shroud 184. A lightweight ball 192which will normally occupy the lower end of housing 194, will, under theeffect of a rising airflow through the housing 194, rise to engage andclose off the opening 190 as shown in dotted outline at 192′.

[0095] The rapid circulation of air around 180 will tend to separateparticles in the airstream from the air by virtue of centrifugal forces,so that the particles will migrate to the wall of the housing 178 andfall under gravity, past the shroud 188, into the particle collatingregion 196 of the housing 178. The latter is in two parts, the upperpart 180 and the lower part 196, and the latter has a handle 198 toassist in carrying it when full to be emptied.

[0096] The vacuum-source 176 inducing an airflow through 174, does sovia the openings 186, so that the incoming airflow will eventuallychange direction and pass through the openings 188 and pass via thehollow interior of the shell 184 and vortex actuator 180 into a manifold200 which has an exit at 201 from where the now largely particle-freeair is conveyed via a pipe (not shown) to an inlet 202 of a furtherseparation stage contained within a cylindrical housing 204 mountedcoaxially above the housing 178 and manifold 200. The housing 204includes a first downwardly extending frusto-conical axial extension 203which leads to a second frusto-conical member 206. The interior of 204communicates with the particle collecting bin 196 when the ball valve190, 192 is open, and the frusto-conical member 106 provides thefrusto-conical surface 85 previously referred to.

[0097] Centrally of the housing 204 is a downwardly extending tube 208the lower end of which is capped at 210, the cylindrical wall of the capbeing apertured at 212.

[0098] Above the cap 210 is a two-turn helical baffle 214 at the upperend of 204, circumferentially remote from 202 in a second inlet 216 towhich particle-containing air from the third stage is returned.

[0099] Although a helical baffle has been shown as required above theball valve in FIG. 3, it has been found that provided there is asufficient distance between the underside of 210 and the opening 190 inFIG. 5, no helical baffle is required in the FIG. 5 arrangement.

[0100] The tube 208 serves as the air outlet from 204 and the airstreampassing up through 208 is circularly deflected in all directions by adownwardly facing conical end 218 of a cylindrical closure of an axiallyextending tubular member 220 in a cylindrical housing 222. Thecylindrical wall of the closure is apertured as at 224 to provide anexit from the interior of 222, to the suction source 176.

[0101] Particle-containing air from 208 tends to give up the particlesas the air deflected in a radial sense on meeting the conical end face218 abruptly changes direction and returns in a radial sense towards theopenings in the cap 218 as it meets the interior of the housing 222.Particles will tend to be drawn into the lower end of a three turn helix226 and after traversing the helix the particles leave the housing 222via exit 228 to be returned via a pipe (not shown) to inlet 216 inchamber 204, to mix with the incoming particle laden air from 202, to beseparated therefrom by once again travelling the helix 214 and thevortex travelling to and from the lower end of 206..

[0102] Substantially particle free air exits via the openings 224through tube 220 to the suction source 176 and it is found that overallseparation can be so effective that there is no need for any filter inthe path through 220 to the source 176.

[0103] As shown in FIG. 6, the ball is freely contained within acylindrical housing 194 the upper end 230 of which is sealingly securedto the lower open end of the shroud 184 of FIG. 3. Radial protrusions232, 234 prevent the ball from falling through the lower open end of thehousing 194—and as shown in FIG. 7, four such radial protrusions areprovided, 232, 234, 236 and 238. Near the open upper end of the housing194 is an annular protrusion 240 which forms a valve seat whichco-operates with the ball 192 to close off the passage of air throughthe opening 242 defined by the annular protrusions 240, when the ball islifted (as by airflow in an upward sense) when vacuum is first appliedto the system.

[0104] Where the diameter of the ball 192 is somewhat less than that ofthe interior of the housing 194, particles which collect above the ball192 (when in its upper position shown at 192′) can fall past the balland out through the spaces such as 244, 246, 248 and 250, to exit thehousing into the bin 196.

[0105] A level sensing device (not shown) may be incorporated into thedesign of separator shown in FIGS. 5 to 7.

[0106]FIGS. 7 and 8 illustrate how a different type of valve from thatshown in the earlier Figures, can be used. The valve is located in ahousing 251 and comprises a conical poppet 252 at the lower end of aspindle 254 at the upper end of which is a cup 256. A valve seating 258retains an O-ring 260 against which the conical surface of the poppet252 is forced, to close the valve once the airflow has been establishedthrough the apparatus. The spindle 254 extends through the poppet and isslidingly received in a guide 262 in a cross member 264 which extendsacross the lower end of the housing 251. The cross member 264 and guide262 are shown in the scrap view of FIG. 8A.

[0107] Particles can pass down through the open end of tube 30 or 185(see FIGS. 1 and 5) during operation, and remain above the poppet 252until airflow ceases, whereupon the poppet drops and particles can fallpast the conical surface of the poppet and around the cross member 264,into the common bin 14.

[0108] A spring (not shown may be fitted between the conical surface 252and the upper end 266 of the enclosure 251, (or between the cup 256 andthe end 266) so that as soon as airflow drops, the poppet valve opensunder the action of the spring.

[0109] The apparatus described herein may also be used for separatingliquids (eg water) from gases (eg air) since in general liquids are moredense than gases. If solid particles are also present of material havinga density greater than the gaseous and liquid phases, these can also beseparated from the gaseous phase along with the liquid phase, and in asecond pass through the apparatus or by passage through a second similarapparatus, the solids can be separated from the liquid phase, providedthe relative densities are sufficiently different.

[0110] In any situation where liquid is involved, a liquid trap orfilter may be provided if the suction source would become contaminatedor damaged by liquid reaching it, such as if it comprises a fan drivenby an electric motor, or steps may be taken to separate any liquid fromthe motor. Alternatively a non-electric pump may be used which is notaffected by the passage of liquid therethrough.

[0111] Where a helix is shown in any of the drawings the angle of thehelix is typically in the range 20° to 10° and preferably of the orderof 4°.

1. Apparatus for separating particulate material from an airstreamestablished by suction, comprising: (1) a primary separation chamber inwhich particles are separated from the airstream therein by centrifugalforce; (2) a main particle collecting region into which the particlesseparated by the primary separation can fall under gravity; (3) asecondary separation chamber downstream of the primary chamber, to whichair and particles not separated in the first chamber, pass; (4) an airoutlet in the secondary chamber through which air substantially free ofparticles can exit; (5) an intermediate particle collecting regionassociated with the secondary chamber, in which particles collect afterseparation by centrifugal force from the air flowing through thesecondary chamber; (6) a valve between the intermediate particlecollecting region and a second particle collecting region, having avalve closure member which closes the valve while air flows through theapparatus but which opens the valve when airflow ceases, to allowparticles in the intermediate region to pass into the second region;characterised in that the valve closure member presents a conical orfrusto-conical surface to an annular seating which includes an O-ringagainst which the said surface engages when the valve is closed. 2.Apparatus as claimed in claim 1, wherein the second collecting region isseparate from the main particle collecting region.
 3. Apparatus asclaimed in claim 1 wherein the main particle collecting region alsocomprises the second particle collecting region.
 4. Apparatus as claimedin any of claims 1 to 4 in which the valve means is operable manually.5. Apparatus as claimed in any of claims 1 to 3 in which the valve meansis operable electrically.
 6. Apparatus as claimed in any of claims 1 to3 in which the valve operates in response to the flow of air through theapparatus so as to become closed when the air flow reaches and exceeds agiven rate of flow, and opens when air fluid flow falls below a givenrate of flow.
 7. Apparatus as claimed in claim 1 or 2 in which a baffleis located between the intermediate and second regions to create atortuous path for particulate material therethrough.
 8. Apparatus asclaimed in claim 7 in which the baffle is a helix.
 9. Apparatus asclaimed in claim 8 in which the entry point of the helix is spaced fromthe exit from the secondary separation chamber.
 10. Apparatus as claimedin claim 9 wherein the gap between the entrance to the helix and theexit from the secondary separation chamber is in the range 4 to 6.4 mm.11. Apparatus as claimed in claim 8, 9 or 10 in which the helix has twocomplete turns.
 12. Apparatus as claimed in any of claims 7 to 11 inwhich a gap of the order of 4 mm exists between the ball and a valveseating, when open.
 13. Apparatus as claimed in any of claims 1 to 12,wherein spring means acts on the closure member in a direction tomaintain the valve open.
 14. Apparatus as claimed in any of claims 1 to13 further comprising a level sensing device in the or each particlecollecting region to indicate when the contents of the collecting regionhas reached a given level, requiring it to be emptied.
 15. Apparatus asclaimed in claim 14 in which the sensing device includes a switchgenerating an alarm and/or for interrupting the power supply to thesuction producing means.
 16. Apparatus as claimed in any of claims 1 to15 characterised in that the air is replaced by a liquid and thematerial to be separated therefrom is particulate material or anothermore dense liquid.
 17. Apparatus constructed and adapted to operatesubstantially as herein described with reference to and as illustratedin the accompanying drawings.